1. Field
The present disclosure relates to tire vulcanizing molds and, more precisely, to molds of the type having sectors. Vulcanizing molds vulcanize the tire by applying pressure and heat to a tire blank. Vulcanizing molds of the type having sectors are produced as a plurality of components that are assembled and driven by appropriate kinematics in conjunction with the curing press.
2. Description of Related Art
Vulcanizing molds generally comprise sectors that can move radially relative to the axis of the mold. In a vulcanizing mold of this type, the molding space of the exterior surface of the tire is defined by two shells, each one molding a sidewall, and by a ring of sectors or two rings of half-sectors for molding the tread. In vulcanizing molds with radially movable sectors, the sectors are entrained in a radial movement usually by the axial movement of an inclined component, generally a closure ring having an interior surface of frustoconical form that collaborates with the radially exterior surface of frustoconical form of the sectors.
During vulcanizing, the tire blank is subjected to certain conditions of pressure and temperature that cause the unprocessed rubber mixture to become fluid. In order to prevent the formation of molding burrs, the parting lines have to remain leaktight. The lining used to mold the tread is generally produced from an aluminium alloy, using casting techniques. When the mold is clamped in the vulcanizing press to close the sectors, particularly where there is an excessive clamping force, there will be the appearance of crushing phenomena at the aluminium interfaces of the linings and of the steel shells. As the aluminium linings are less resistant than the shells, crushing of the linings gives rise to damage to the mold, resulting in a reduction in its service life and even compliance issues in the case of the tires produced using this mold.
Document EP 0522374, in the name of one of the applicants, relates to the problem of leaktightness between the sectors and proposes a mold composed of two shells and a ring of sectors, each sector comprising a support and a molding lining, and wherein the molding lining is affixed to the support by strips in the form of an arc of a circle, each bearing on one of the ends of the support. Thus, when the mold is in the closed position, the sectors are in contact with one another via the strips that likewise ensure contact between the sectors and the shells, the strips being in elastic compression by virtue of bearing on one another. This document admittedly provides a solution to the problem of leaktightness between sectors but, in order for the mold to be leaktight at the molding joints, requires an adaptation of the linings at the perimeter formed by the strips for affixing the linings. This adaptation is achieved by means of a perimeter shortening of all the molding linings upon first closure of the mold, requiring residual deformation of the linings with, when manufacturing tolerances are excessive, residual tension in the linings. Moreover, this solution requires the use of strips that are additional molding components that make it possible to counter the press forces with a view to limiting crushing of the aluminium linings and thus the reduction in the diameter of the mold generated in order to guarantee the leaktightness of the sectors. These strips thus constitute supplementary interfaces in the tire molding zone and require a high level of operational precision if rubber burrs are to be eliminated.
One solution has been described in document JP 2010-076344, in which a circumferential clearance has been provided between adjacent sectors to compensate for their expansion.